Author
Topic: Jack multichannel - setting alsa to use more than one system capture/playback (Read 6662 times)

Hi. Before I start, forgive me for any grammatical error. I can well understand, but not write well in English. Ok, let's go.

I use Ubuntu 9.04 and Debian Lenny. I'm a linux user since 2007.

I've tried without success, using jackd and through qjacktl interface, use the default capture of my notebook (VAIO VGN NW 130J, microfone entrance) combined with a microfone of the USB sound card. The qjacktl interface returns me only the system microfone capture and the default playback. I would like to use both of them, to be abble to use separated audio software treatment via Jamin, Creox, Jack-Rack etc, and separately get audio signal from each card.

I've read those links a lot. I guess I've lost some important thing about the configuration. If I'm not wrong, ALSA will create a virtual drive that includes both cards. This appears sort of obscure to me.

under a Real Time Kernel, I obtained good results (in terms of latency - 10.7 ms and a few xruns) to use that in live audio treatment, just like Shows and general events.But this do not allow me individual audio signal treatment: The voice signal of microfones deserves some echo and equalization. For the guittars, I want to equalize them separately. The same as the bass and keyboards (just examples).

Sooner or later, I will get a Delta 1010 sound card or something like, but I want to know how to configure alsa; also, for personnal understanding.

Yes, I've tried that before. The USB sound card is correctly recognized and work fine, but it's necessary to choose it instead the default capture. In other words, it's the same when using the default capture. Just one stereo channel capture, and so playback.

Also, I'm testing a clean instalation of Ubuntu with a real time kernel. The results are great, I can use my notebook instead the traditional equalizer, with the obviously vantage of ladspa plugins. I think about buy a Delta 1010 for my PC and use it, but will be necessary to configure the .asoundrc for the multiple inputs of the sound card.

This is the link to the ALSA project, and it could explain more effectively the .asoundrc. What happens is that it's possible to create this virtual drive that I've said. The advantage is that we can customize the sound features (start the jack with xxxxxx sample rate etc). In the alsa project we have some examples.

Also, it's possible combine 2, 3 or more sound cards to multiply the audio connection and set the definitions. For example, with the virtual drive, we can create a mini-drive with just 4 in/out, even with the Delta 1010, and ignore the rest.

In fact, Ubuntu is the perfect platform for audio treatment. It's amazing what we can do with a real time kernel and some open source apps. I cannot find, in Windows, application that allow me to do what I do in Linux (Ubuntu, mostly) without a powerfull hardware. I'm writting a how-to about real time audio treatment and equalization. A deserved contribution for the community that has always provided me knowledge. If I succed to configure the asoundrc, my how-to will be finished (also, my project). I'm working in the English version too...

Excuse-me joe12, I'm not sure if I understood this last phrase: "so long as you tell ubuntu to use the Delta ??".

About to use every inputs and outputs, the recognizing is not automatically, according what I read in these links above. But I'm not sure, I've not tested yet, since I don't have a Delta1010.

In any case, I want to learn how to configure it for the case of multiple sound cards, and in this case, for a USB sound card. In fact, a lot of USB sound cards. It will be usefull for the Delta1010 too, because it's necessary to edit the .asoundrc.

I know what your problem is, and I'm sure of that because I want to do exactly the same: multiple USB soundcards on ALSA.

I think the main problem is the channel number you set on pcm.multi_capture. I don't know if you're aware of this information, but this USB soundcard you have (which I have a similar one) is STEREO output and MONO input, meaning that it has dual-channel playback and ONLY single-channel recording.

PM me if you had advanced or still have interest in this specific topic. I am working on a university project that is leading me to this same multiple USB soundcards issue.